01 - Preheat oven to 350°F. Line 2 baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, and salt until evenly distributed.
03 - In a large bowl, beat the softened unsalted butter, granulated sugar, and light brown sugar using an electric mixer until light and creamy, about 2 to 3 minutes. Add the egg and vanilla extract, then mix until fully combined.
04 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed just until the dough comes together. Avoid overmixing.
05 - Scoop 1 tablespoon of dough and flatten it slightly in your palm. Place 1/2 teaspoon of strawberry jam in the center and cover with another tablespoon of dough. Pinch the edges together to seal completely, then gently roll into a smooth ball. Repeat with the remaining dough and jam.
06 - Place the filled cookie dough balls onto the prepared baking sheets, spacing them about 2 inches apart to allow for spreading.
07 - Bake for 12 minutes or until the edges are lightly golden. Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
08 - In a small bowl, whisk together the powdered sugar, milk, vanilla extract, and a drop of food coloring if desired, until smooth and slightly thickened. Spread the glaze over the fully cooled cookies and top with rainbow sprinkles. Allow the glaze to set before serving.